This invention relates to air heating furnace systems having means to store, and subsequently release, heat from the flue gas which would otherwise be merely dissipated through the stack; and more particularly to a heat storage exchange unit for association with the flue gas stack of such furnace systems.
Much thought has been given to increase in the efficiency of furnaces for the heating of building space, particularly furnaces which are heated by oil or gas, by utilizing the heat of the flue gases which is otherwise lost.
This invention is concerned with a forced air heating furnace, wherein the fuel is a flowable fuel the flow of which may be controlled, including a primary heat exchanger wherein heat of the burning fuel is transferred to the circulated air, and a recuperator exchanger for storing heat removed from the flue gas and later transferring the stored heat to the circulated air, with the two heat exchangers being operated alternatively to heat the circulated air as required.
More specifically, this invention is concerned with the use of a phase change heat storage material in the recuperator exchanger, to enable the maximum transfer of heat from the flue gas to the storage material and the maximum transfer of heat from the storage material to the circulated air.
A primary object of this invention is to provide a heating furnace system which will operate at much higher efficiency than conventional heating furnace systems.
Another object of this invention is to provide an auxiliary system which may be added to an existing heating furnace system, without major change in the existing system, to produce a much more efficient overall furnace system.
Another object of this invention is to provide a heating furnace system including a second recuperator exchanger in association with the flue gas stack, wherein a phase change material is used as a heat storage and heat recovery medium.
Still another object of this invention is to provide a heating furnace system, utilizing a recuperator exchanger associated with the stack of the furnace system, and which is much more efficient and effective than known systems utilizing a second heat exchanger associated with a furnace stack.
A still further object of this invention is to provide a novel heat recuperator exchanger for association with the flue gas stack of a furnace system to produce a much more efficient furnace system.
These objects are accomplished in a forced air heating system comprising the following components:
A furnace includes a combustion chamber for burning a flowable fuel as a source of heat, means for controlling the flow of fuel to the combustion chamber, inlet duct means and discharge duct means for the circulated air flowing through the furnace, a primary heat exchanger for the circulated air associated with the combustion chamber, and a stack for discharging flue gas from the primary heat exchanger. A blower effects the flow of circulated air through the furnace and through the space to be heated. A recuperator exchanger comprises a body of a phase change material, disposed in heat exchange relation with the flue gases flowing through the stack, and means for conveying the circulated air in heat exchange relation with the heat exchange body. Duct means connect the recuperator exchanger between the inlet duct means and the outlet duct means. A bypass duct means is connected between the inlet duct means, for bypassing the recuperator exchanger. A gate means effects the flow of circulated air alternatively through the recuperator exchanger and the bypass duct means. An actuator means is responsive to the temperature of the phase change material, for controlling the fuel flow control means and for controlling the gate means.